1. Field of the Invention
This invention relates to conductive foil printed circuit patterns which are laminated to flexible dielectric strip carriers. More particularly, this invention is concerned with flexible sprocketed lead frame tape having a plurality of printed circuit patterns arranged in a plurality of planes and interconnected to components to provide active electronic modules.
The novel printed circuit tape of the present invention is adapted to be supplied in reel form to be used on bonding machines and assembly machines for automatic and semiautomatic production of electronic modules.
2. Description of the Prior Art
In U.S. Pat. No. 3,696,229 there is provided a lead frame carrier having a printed circuit lead frame thereon, which is bonded to raised conductive bumps on an active component. The disclosed method involves aligning electrical leads on the carrier with corresponding contacts and bumps on the active component and then thermocompression bonding the aligned leads to the contacts or bumps. The bonded active component and the pattern having the electrical leads is subsequently separated from the lead frame carrier to provide a beam lead device for assembly on a printed circuit board or substrate. Accordingly, this patent discloses the connection of an active component to a single layer printed circuit carrier or tape.
In U.S. Pat. No. 3,838,984, there is provided a printed circuit lead frame carrier, having electrically conductive gold bumps which extend through via holes in the carrier tape. The gold bumps are connected to the underside of a copper foil lead frame pattern and are extended through the carrier tape and protrude from the opposite side. The gold protrusions or bumps on the flexible tape are adapted to be connected to electrical contacts on an active semiconductor device. The assembly, when stripped or cut from the carrier, provides a beam lead device. In a similar manner, U.S. Pat. No. 3,868,724 teaches an improved technique for plating the gold bumps through via holes to provide an improved beam lead device.
In the electronic data processing field, the main printed circuit boards for receiving both memory and logic printed circuit cards comprise multiple layers of printed circuit patterns. Elaborate and diverse means are employed to connect selective area of one of the conductive printed circuit planes to another printed circuit plane. The most common via connections comprise plated-through holes, pins, rivets and jumper wires. Such multiple layer printed circuit boards are individually assembled, rigid structures. Rigid multilayer printed circuit boards are not provided with flexible leads, however, flexible wires are connected to such rigid printed circuit boards to interconnect components mounted thereon, or to interconnect the printed circuit board into a circuit system.
Printed circuits have been applied to the opposite sides of a single layer rigid board and to a single side of single layer rigid or flexible substrates. The means employed for making interconnections on such boards or substrates have been the same as those employed in making interconnections on the aforementioned rigid multilayer printed circuit boards namely, jumper wires, plated-through holes, rivets and/or pins. Heretofore, such single layer printed circuits have not been adaptable to provide single layer sprocketed flexible tapes, which would permit continuous automatic production.
Heretofore, miniature rigid printed circuit boards and substrates have been employed for the assembly of modules, but have required individual miniature wire bonds to interconnect active compounds and/or connection points.
Heretofore, miniature sprocketed lead frame carrier tapes have been employed for the assembly of discrete components, but have not been employed for the assembly of electronic modules.
Hybrid modules employed in the electronic watch and electronic calculator industry, have heretofore been assembled individually on rigid substrates.
Heretofore, electronic module assemblies were individually assembled in a manner which required a high labor content. Such electronic modules as are assembled for watches, and calculators are known to be extremely fragile when employing ceramic substrates. Individual handling and individually wire bonding of the electronic modules for watches and calculators has produced a high rejection rate. Attempts to produce higher yields have often resulted in passing through inspection marginal or unreliable modules. When electronic modules are assembled individually, there is little or no possibility of incorporating automatic or semiautomatic machines in the production line to increase production. Electronic modules, which are assembled on rigid circuit boards usually require more wire bonds and interconnection wires than are actually necessary.